Therefore, the higher activity of 1 can be attributed to its
special structure matching with the phosphodiester backbone of
nucleic acid and cooperative interaction from the highly active
(bipy)2CuII–H2O moiety and two positive pendants. For complex
2, the large butyl groups probably prevent nucleophilic attack
of the (bipy)2CuII–OH moiety to phosphodiester and therefore
results in its lower nuclease activity.
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Conclusion
Although complexes 1 and 2 have similar Cu(II) structural
configurations, 1 exhibits higher nuclease activity and give ca.
10-fold rate acceleration for hydrolyzing the phosphate diesters
relative to 2 and its unmodified analogue. The unique acceleration
could be attributed to the presence of the two positive pendants.
If pendants have too large steric groups, however, the hydrolysis
rate constants of DNA cleavage not only cannot increase but also
markedly decrease. What is clearly of significance is that these
models structurally match with the phosphodiester backbone of
nucleic acid.
24 S. C. Zhang, Y. Shao, C. Tu, C. H. Dai and Z. J. Guo, Chin. J. Inorg.
Chem., 2004, 20, 1159.
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27 D. Y. Kong, J. Reibenspies, J. G. Mao, A. Clearfield and A. E. Martell,
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Acknowledgements
28 L. Zhu, O. dos Santos, C. W. Koo, M. Rybstein, L. Pape and J. W.
Canary, Inorg. Chem., 2003, 42, 7912.
29 L. M. Rossi, A. Neves, R. Horner, H. Terenzi, B. Szpoganicz and J.
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This work was supported by the National Natural Science
Foundation of China (Grant No: 20231010, 20529101), Ministry
of Education of China and the Guangdong provincial Natural
Science Foundation (04009703). We are especially thankful to
Prof. Hongzhe Sun (Hong Kong University) for valuable dis-
cussions and Prof. Xiao-Ming Chen for providing access to low-
temperature CCD equipment.
32 G. N. De Iuliis, G. A. Lawrance and S. Fieuw-Makaroff, Inorg. Chem.
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